From owner-freebsd-current  Tue Oct 20 11:05:57 1998
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From: "Richard Seaman, Jr." <lists@tar.com>
To: "Jason Evans" <jasone@canonware.com>
Cc: "current@freebsd.org" <current@FreeBSD.ORG>
Date: Tue, 20 Oct 98 13:05:03 -0500
Reply-To: "Richard Seaman, Jr." <lists@tar.com>
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Subject: Re: Another Serious libc_r problem
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On Mon, 19 Oct 1998 18:03:22 -0700 (PDT), Jason Evans wrote:

>Hmm, your test case is very similar to some code that was causing deadlock
>for me.  However, I boiled it down to the following code as being the
>actual bug.  We may be seeing the same thing (but maybe not; I haven't had
>time to dig into this all the way).
>
>Jason

I think the problem in your code is that you expect to be able to recursively
lock a mutex in the same thread, using the default mutex type.  I don't
think this is a bug, since the "default" mutex type is implementation
defined, if I'm not mistaken.

Try the following adjustments to your code:

/* -*-mode:c-*- */
#ifndef _REENTRANT
#  define _REENTRANT
#endif
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
int
pthread_mutexattr_setkind_np(pthread_mutexattr_t *attr, int kind);
  
int
main()
{
  pthread_mutex_t mutex;
  pthread_mutexattr_t attr;
  int error;
  pthread_mutexattr_init (&attr);
  pthread_mutexattr_setkind_np (&attr, MUTEX_TYPE_COUNTING_FAST);
  error = pthread_mutex_init(&mutex, &attr);
  pthread_mutexattr_destroy (&attr);
  if (error)
  {
    fprintf(stderr, "Error in pthread_mutex_init(): %s\n", strerror(error));
    exit(1);
  }
  fprintf(stderr, "About to lock mutex first time.\n");
  error = pthread_mutex_lock(&mutex);
  if (error)
  {
    fprintf(stderr, "Error in pthread_mutex_lock(): %s\n", strerror(error));
    exit(1);
  }
  fprintf(stderr, "About to lock mutex second time; expect deadlock.\n");
  error = pthread_mutex_lock(&mutex);
  if (error)
  {
    fprintf(stderr, "Error in pthread_mutex_lock(): %s\n", strerror(error));
    exit(1);
  }
  fprintf(stderr, "Wow, no deadlock.\n");
  error = pthread_mutex_destroy(&mutex);
  if (error)
  {
    fprintf(stderr, "Error in pthread_mutex_destroy(): %s\n", strerror(error));
    exit(1);
  }
  
  return 0;
}




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